import * as T from "../../../base/lib/types"
import * as child_process from "child_process"
import * as fs from "fs/promises"
import { Affine, asError } from "../util"
import { ExtendedVersion, VersionRange } from "../../../base/lib"
import { InitKind, InitScript } from "../../../base/lib/inits"

export const DEFAULT_OPTIONS: T.SyncOptions = {
  delete: true,
  exclude: [],
}
export type BackupSync<Volumes extends string> = {
  dataPath: `/media/startos/volumes/${Volumes}/${string}`
  backupPath: `/media/startos/backup/${string}`
  options?: Partial<T.SyncOptions>
  backupOptions?: Partial<T.SyncOptions>
  restoreOptions?: Partial<T.SyncOptions>
}

export type BackupEffects = T.Effects & Affine<"Backups">

export class Backups<M extends T.SDKManifest> implements InitScript {
  private constructor(
    private options = DEFAULT_OPTIONS,
    private restoreOptions: Partial<T.SyncOptions> = {},
    private backupOptions: Partial<T.SyncOptions> = {},
    private backupSet = [] as BackupSync<M["volumes"][number]>[],
    private preBackup = async (effects: BackupEffects) => {},
    private postBackup = async (effects: BackupEffects) => {},
    private preRestore = async (effects: BackupEffects) => {},
    private postRestore = async (effects: BackupEffects) => {},
  ) {}

  static ofVolumes<M extends T.SDKManifest = never>(
    ...volumeNames: Array<M["volumes"][number]>
  ): Backups<M> {
    return Backups.ofSyncs(
      ...volumeNames.map((srcVolume) => ({
        dataPath: `/media/startos/volumes/${srcVolume}/` as const,
        backupPath: `/media/startos/backup/volumes/${srcVolume}/` as const,
      })),
    )
  }

  static ofSyncs<M extends T.SDKManifest = never>(
    ...syncs: BackupSync<M["volumes"][number]>[]
  ) {
    return syncs.reduce((acc, x) => acc.addSync(x), new Backups<M>())
  }

  static withOptions<M extends T.SDKManifest = never>(
    options?: Partial<T.SyncOptions>,
  ) {
    return new Backups<M>({ ...DEFAULT_OPTIONS, ...options })
  }

  setOptions(options?: Partial<T.SyncOptions>) {
    this.options = {
      ...this.options,
      ...options,
    }
    return this
  }

  setBackupOptions(options?: Partial<T.SyncOptions>) {
    this.backupOptions = {
      ...this.backupOptions,
      ...options,
    }
    return this
  }

  setRestoreOptions(options?: Partial<T.SyncOptions>) {
    this.restoreOptions = {
      ...this.restoreOptions,
      ...options,
    }
    return this
  }

  setPreBackup(fn: (effects: BackupEffects) => Promise<void>) {
    this.preBackup = fn
    return this
  }

  setPostBackup(fn: (effects: BackupEffects) => Promise<void>) {
    this.postBackup = fn
    return this
  }

  setPreRestore(fn: (effects: BackupEffects) => Promise<void>) {
    this.preRestore = fn
    return this
  }

  setPostRestore(fn: (effects: BackupEffects) => Promise<void>) {
    this.postRestore = fn
    return this
  }

  addVolume(
    volume: M["volumes"][number],
    options?: Partial<{
      options: T.SyncOptions
      backupOptions: T.SyncOptions
      restoreOptions: T.SyncOptions
    }>,
  ) {
    return this.addSync({
      dataPath: `/media/startos/volumes/${volume}/` as const,
      backupPath: `/media/startos/backup/volumes/${volume}/` as const,
      ...options,
    })
  }

  addSync(sync: BackupSync<M["volumes"][0]>) {
    this.backupSet.push(sync)
    return this
  }

  async createBackup(effects: T.Effects) {
    await this.preBackup(effects as BackupEffects)
    for (const item of this.backupSet) {
      const rsyncResults = await runRsync({
        srcPath: item.dataPath,
        dstPath: item.backupPath,
        options: {
          ...this.options,
          ...this.backupOptions,
          ...item.options,
          ...item.backupOptions,
        },
      })
      await rsyncResults.wait()
    }

    const dataVersion = await effects.getDataVersion()
    if (dataVersion)
      await fs.writeFile("/media/startos/backup/dataVersion.txt", dataVersion, {
        encoding: "utf-8",
      })
    await this.postBackup(effects as BackupEffects)
    return
  }

  async init(effects: T.Effects, kind: InitKind): Promise<void> {
    if (kind === "restore") {
      await this.restoreBackup(effects)
    }
  }

  async restoreBackup(effects: T.Effects) {
    this.preRestore(effects as BackupEffects)

    for (const item of this.backupSet) {
      const rsyncResults = await runRsync({
        srcPath: item.backupPath,
        dstPath: item.dataPath,
        options: {
          ...this.options,
          ...this.backupOptions,
          ...item.options,
          ...item.backupOptions,
        },
      })
      await rsyncResults.wait()
    }
    const dataVersion = await fs
      .readFile("/media/startos/backup/dataVersion.txt", {
        encoding: "utf-8",
      })
      .catch((_) => null)
    if (dataVersion) await effects.setDataVersion({ version: dataVersion })
    this.postRestore(effects as BackupEffects)
    return
  }
}

async function runRsync(rsyncOptions: {
  srcPath: string
  dstPath: string
  options: T.SyncOptions
}): Promise<{
  id: () => Promise<string>
  wait: () => Promise<null>
  progress: () => Promise<number>
}> {
  const { srcPath, dstPath, options } = rsyncOptions

  await fs.mkdir(dstPath, { recursive: true })

  const command = "rsync"
  const args: string[] = []
  if (options.delete) {
    args.push("--delete")
  }
  for (const exclude of options.exclude) {
    args.push(`--exclude=${exclude}`)
  }
  args.push("-actAXH")
  args.push("--info=progress2")
  args.push("--no-inc-recursive")
  args.push(srcPath)
  args.push(dstPath)
  const spawned = child_process.spawn(command, args, { detached: true })
  let percentage = 0.0
  spawned.stdout.on("data", (data: unknown) => {
    const lines = String(data).replace("\r", "\n").split("\n")
    for (const line of lines) {
      const parsed = /$([0-9.]+)%/.exec(line)?.[1]
      if (!parsed) continue
      percentage = Number.parseFloat(parsed)
    }
  })

  spawned.stderr.on("data", (data: unknown) => {
    console.error(`Backups.runAsync`, asError(data))
  })

  const id = async () => {
    const pid = spawned.pid
    if (pid === undefined) {
      throw new Error("rsync process has no pid")
    }
    return String(pid)
  }
  const waitPromise = new Promise<null>((resolve, reject) => {
    spawned.on("exit", (code: any) => {
      if (code === 0) {
        resolve(null)
      } else {
        reject(new Error(`rsync exited with code ${code}`))
      }
    })
  })
  const wait = () => waitPromise
  const progress = () => Promise.resolve(percentage)
  return { id, wait, progress }
}